Nonlinear DC and dispersive conductivity of ion conducting glasses and glass ceramics

Abstract

Frequency-dependent third-order conductivity spectra σ′ 3(v) of various ion conducting glassesand glass ceramics were obtained by applying sinusoidal electric fields with high amplitudesand by analysing the resulting higher-harmonic currents. In the DC conductivity regime, thethird-order conductivity σ3, dc was found to be positive for all materials and at all temperatures.From the ratio of the third-order conductivity to the low-field conductivity, σ3, dc/σ 1, dc apparentjump distanceswere calculated. These apparent jump distances are much larger than jump distancesbetween neighbouring sites in the glasses and decrease with increasing temperature. In(Li2O) 1-x ̇(Na2O)x ̇Al 2O3 ̇ (SiO2)4 glasses, themixed alkali effect leads to a minimumin theapparent jump distance, while partial crystallisation of Li2ȮAl2O3 ̇ (SiO2)2 glasses leads toan increase of the apparent jump distance. In the dispersive regime, the third-order conductivityσ′ 3(v) of all glasses and glass ceramics is negative and exhibits an approximate power-lawdependence, however with a larger exponent than the dispersive low-field conductivity σ′1(v).For a given material, the third-order conductivity spectra σ′3(v) obey the time-temperature superpositionprinciple and can be superimposed by using the Summerfield scaling.Remarkably,the shift between the σ′ 3(v) master curves of different materials is much stronger than the shiftbetween the σ′ 1 (v) master curves. In order to rationalize this effect, we calculate the nonlineardispersive hopping conductivity in a doubleminimum potential approximation. © by Oldenbourg Wissenschaftsverlag, München.